Fibrous products are used for numerous industrial purposes, such as for making insulation products, structural products, reinforcement products, decorative products, etc. Insulation products include thermal insulation products, which block heat flow, and acoustical insulation products which can have either a sound-barrier quality to block the transmission of sound or a sound-absorptive quality to dissipate or absorb sound, or both a sound-barrier quality and a sound-absorptive quality. Examples of fibrous thermal and/or acoustical insulation products, are pipe insulators used to prevent heat and/or sound passage from the inside of the pipe to the surrounding air. Such pipe insulators may be used, for instance, in a muffler of an automobile exhaust system. Typically, pipe insulators are hollow tubular fibrous products made from glass wool.
One method for manufacturing a pipe insulator from glass wool comprises the following steps: manufacturing a tape of glass wool containing a binder; folding the tape into a tubular shape (by bringing the longitudinal edges of the tape into contact with each other) by means of a folding shoe through which the tape is passed, thereby forming a tube of glass wool; and advancing the tube through a mold while passing hot curing gases through the tube to cure the binder, thereby forming the pipe insulator. Typically, the glass wool tape is folded around a central mandrel, this mandrel being perforated for the passage of the hot curing gases. Such a method is disclosed, for instance, in U.S. Pat. No. 4,564,486 and U.S. Pat. No. 6,319,444.
One drawback of this method is that folding the glass wool tape into a tubular shape having a cross-section different from a circular one, may be difficult. Another drawback is that bringing and bonding the longitudinal edges of the tape together may be difficult and creates a bonding interface between these longitudinal edges, such an interface affecting the overall insulation properties of the pipe insulator.
Another method, disclosed in U.S. Pat. No. 4,569,471, comprises the following steps: providing a container consisting of an outer cylinder, a perforated inner tube and a first end cap; blowing glass wool with compressed air into the container, for filling the container with the glass wool, while sucking the air out of the inside of the container by means of a suction fan, via the perforations of the inner tube; and welding a second end cap on the container.
One drawback of this other method is that the glass wool has a natural tendency to expand and come out of the container (even when suction is applied) and, therefore, the glass wool often spreads over and soils the welding area for the second end cap.
Thus, there remains a need in the art for additional methods of producing fibrous products.